Ultrasonic motor using bending, longitudinal and torsional vibrations

Abstract

An ultrasonic motor having a cantilever type longitudinal/torsional vibration coupling element with a beam and a rotor rotated by the vibration of the beam. The rotor is provided with contacting surface for only contacting the beam in the outer peripheral portion of the surface of the beam away from the torsional vibration axis of the beam.

What is claimed is: 
     
       1. An ultrasonic motor comprising a stator including a bending vibration plate, a longitudinal and torsional vibration coupling element having a beam extending slanted relative to the vibration axis of the bending vibration plate, a piezoelectric thickness vibration element connected with the longitudinal and torsional vibration coupling element through an elastic vibration element, a longitudinal vibration element combined with the longitudinal and torsional vibration coupling element, the elastic vibration element and the piezoelectric thickness vibration element, said beam of the stator generating elliptical vibration which is combination of longitudinal vibration generated in the piezoelectric thickness vibration elements and then boosted in the elastic vibration element and torsional vibration generated in the longitudinal and torsional vibration coupling element excited by the longitudinal vibration and therefore having the same frequency of the vertical vibration, and a rotor which is contacted with the leg of the stator to receive the elliptical vibration to be rotated, wherein the improvement comprises surface contacting means for contacting with the beam of the stator only in the outer peripheral portion of the surface of the beam away from the torsional vibration axis and depressing means for applying a force to depress the contact surface means to said beam. 
     
     
       2. The motor according to claim 1, wherein said surface contacting means is made of a disc having an annular ring contactable with the beam. 
     
     
       3. The motor according to claim 1, wherein said depressing means have a fulcrum near the center of the beam. 
     
     
       4. The motor according to claim 1, wherein said beam comprises means for holding the rotor so that a part of the vibration component which does not contribute to rotate the rotor works onto the peripheral portion of the rotor as the depressing force. 
     
     
       5. The motor according to claim 4, wherein said holding means is a recess for receiving a rotor having a frustoconical shape. 
     
     
       6. The motor according to claim 4 , wherein said holding means is a recess for receiving a rotor having a semispherical shape. 
     
     
       7. The motor according to claim 4, wherein said holding means is a projection formed in the central portion of the beam in the form of frustoconical shape. 
     
     
       8. The motor according to claim 2, wherein said motor further comprises means for separating the vibration system from the output system so that the vertical component of the ultrasonic elliptical vibration of the stator is not transferred to the output system through the rotor. 
     
     
       9. The motor according to claim 8, said separating means is an elastic material of a large ultrasonic loss mounted on the depressing means. 
     
     
       10. The motor according to claim 1, wherein the direction of rotation of the motor can be changed by changing the frequency of the power applied to the piezoelectric thickness vibration elements.